1. Field of the Invention
The present invention relates to a process for the production of a silage from a fermentable forage by anaerobic fermentation in the presence of a Lactobacillus bacterium.
2. Description of the Prior Art
A silage is the product of anaerobic preservation of a moist forage crop or crop residue by acidification caused by fermentation. Although the exact chemical and biochemical reactions responsible for the production of a stable silage are unknown, the silage fermentation process can be explained by considering only the principal reaction, i.e., the conversion of carbohydrates into organic acids, thereby lowering the pH and preserving the ensiled materials. However, it must be recognized that this is a simplification. The actual process taking place includes many of the known biochemical and microbiological changes which typically occur in fermentation.
The principal aim of preparing silages is the production of a material useful for feeding animals which can be preserved for long periods of time with a minimum loss of nutrients. For some time it has been recognized that silage production is benefited by maintaining anaerobic conditions and by inhibiting clostridia bacteria. Anaerobic conditions are needed in order to inhibit aerobic microorganisms which otherwise would waste the nutrient resources of the feedstuff through oxidative activities. Furthermore, clostridia are known to cause protein destruction under anaerobic conditions, and their activity must be reduced if maximum retention of nutrient value is to occur.
Furthermore, it has also been known that silage fermentations are benefited by the presence of lactate-producing bacteria. Under ideal fermentation condition, the primary product produced from carbohydrates in the forage material is lactic acid. There are two general pathways that lead to the production of lactic acid from carbohydrates by bacteria. The homofermentative pathway involves the conversion of glucose into two molecules of lactate. The heterofermentative pathway involves the conversion of one molecule of glucose into one molecule each of lactate, ethanol, and carbon dioxide. The homofermentative pathway is especially preferred in silage fermentations since all dry matter is preserved for use as a nutrient (i.e., there is no carbon dioxide production) and energy loss is also minimized. In view of these advantages, rapid production of lactic acid by a homolactic pathway as the primary means for acidifying the silage is preferred.
As previously indicated, it is also desirable to minimize the activity of clostridia during the ensiling process. Although clostridial fermentation also produces acids and may eventually result in formation of a silage, nutrient loss is much greater than for lactate ensiling processes. For example, lactic acid itself is converted by clostridia into butyric acid, two carbon dioxide molecules, and two hydrogen molecules (using two lactic acid molecules as starting material). This results in a dry matter loss of more than 50%. Other clostridial pathways result in the degradation of proteins. For example, amino acids are de-aminated or oxidized to produce ammonia and carbon dioxide. In addition to the obvious destruction of nutrients, the production of basic components like ammonia raises the pH of the resulting silage and prevents acid-forming bacteria from reducing the pH to the level required for long-term storage.
Because of the desirability of producing rapid lactic acid production, various publications have suggested inoculating silage feedstuffs with additional latate-producing bacteria. For example, M. E. McCullough, Feedstuffs, 49, 49-52 (1977), suggests desirable characteristics for a potential organism that would be satisfactory for use in silage production. Typical characteristics include the following: (1) the organism should have a high growth rate and be able to compete with and dominate other organisms likely to occur in silage; (2) the organism should be homofermentative; (3) the organism should be acid-tolerant and produce a final pH of 4.0 rapidly; (4) the organism should be able to ferment glucose, fructose, and sucrose, and preferably be able to ferment fructosans and pentosans; and (5) the organism should not react further with organic acids. However, as pointed out in McCullough's article, no organism having all of these desirable characteristics was known. Accordingly, there remains a need for a lactate-producing organism suitable for improving the production of silage from fermentable forage materials.